The 25-year-old has impressed at the Estadio da Luz since leaving Real Madrid in 2009 and has caught the attention of the Premier League champions, who could be about to make a late offer for the player.

However, the Portuguese outfit are demanding offers for the Spaniard to be no less than his £24m buy-out clause.

Club president Pinto da Costa said: "Javi only leaves for this figure. It is non-negotiable."

City have only signed Jack Rodwell from Everton this summer, although the club are thought to be closing in on the capture of Swansea City's Scott Sinclair.